Geared hydraulic apparatus

ABSTRACT

Geared hydraulic apparatus provided with a set of three annular gaskets designed to co-operate partly with a side-plate and partly with the body of the apparatus, in order to form two independent pressure regions respectively connected to the intake and to the discharge of the apparatus, namely a central low pressure region and an outer region kept at a predetermined intermediate pressure. Each side-plate comprises, opposite each of the two passages formed between this side-plate and the adjacent cover by said third gasket and that of the two first gaskets which defines the region in which the pressure is highest, a sealing plug mounted to slide in a sealed manner in a blind hole in the side-plate and urged by relatively high pressure to bear against the cover adjacent the latter in order to seal the corresponding passage.

United States Patent [1 1 Laumont 1 GEARED HYDRAULIC APPARATUS [75] Inventor: Roger Laumont, Nogent-sur-Marne,

France [73] Assignee: Hydroperfect-International H P I,

Chennevieres sur Marne, France [22] Filed: Jan. 24, 1974 [21] Appl. No.: 436,240

[ 1 July 22, 1975 Primary ExaminerC. J. Husar Assistant Examiner-Leonard Smith Attorney, Agent, or Firm-Alan H. Levine [57] ABSTRACT Geared hydraulic apparatus provided with a set of three annular gaskets designed to co-operate partly with a side-plate and partly with the body of the apparatus, in order to form two independent pressure regions respectively connected to the intake and to the discharge of the apparatus, namely a central low pressure region and an outer region kept at a predetermined intermediate pressure. Each side-plate comprises, opposite each of the two passages formed between this side-plate and the adjacent cover by said third gasket and that of the two first gaskets which defines the region in which the pressure is highest, a

sealing plug mounted to slide in a sealed manner in a blind hole in the side-plate and urged by relatively high pressure to bear against the cover adjacent the latter in order to seal the corresponding passage.

5 Claims, 4 Drawing Figures GEARED HYDRAULIC APPARATUS The present invention relates to geared hydraulic apparatus which can be used as pumps or as motors.

In the field of high performance geared hydraulic apparatus, the applicant has already proposed apparatus comprising two co-operating toothed wheels rotatably arranged between two side-plates providing bearings and which are disposed in a cylindrical recess provided in a central body and defined by two opposed covers fixed to the latter in a fluid tight manner, each sideplate having the hydraulic pressure substantially counter-balanced by the provision in corresponding grooves provided in the inner face of the adjacent cover ofa set of three annular gaskets co-operating partly with the side-plate and partly with the body such that two of these gaskets define two independent pressure zones respectively connected to the intake and to the dis charge of the apparatus while the third gasket, which is disposed around the other two, firstly defines with the latter a central low pressure region intended to lubricating the bearings and, secondly with an outer seal provided between the body and the cover, and outer region kept at an intermediate pressure taken from a predetermined point of the apparatus.

During normal use, an apparatus of this type is completely satisfactory, the set of three gaskets inserted in the grooves of each cover making it possible at all times to compensate for and counterbalance the axial effects on the corresponding side-plate of the various hydraulic pressures developed during the rotation of the toothed wheels over a very large range of rotational speeds and delivery pressures. This counter-balancing of the side-plates makes it possible to ensure high volumetric and mechanical efficiency while limiting to the maximum leakages which may occur between the side faces of the two toothed wheels and the opposing faces of the corresponding side-plates.

Nevertheless, in use it has been found that leakages do occur for high delivery pressures, thus reducing the volumetric efficiency of the apparatus. When studied, it appears that these leakages came from the cylindrical space located at the high pressure side between each of the side-plates and the cylindrical recess of the body towards the aforesaid low pressure central region. In fact. in each cover, the space which is doubtless small but indispensable for the obvious reasons of machining grooves in this cover, between said third gasket and that of the first two gaskets which defines thezone in which the pressure is highest, forms a passage connecting the cylindrical recess to the low pressure region limited by this third gasket.

To avoid leakages of this type one may consider replacing each of the two sets of three annular gaskets by a single unitary gasket of a shape similar to that described in French Pat. Specification No. l,426,585 filed on Mar. 9th, 1965 by Mr. Pierre FAVROT, for Improvements applied to the construction of geared hydraulic apparatus particularly used as pumps or as motors." A solution of this type, tested by the Applicant, is nevertheless not adequate because it is not reliable. In fact. the gasket is subject, particularly at the connection of the three branches defining the various pressure regions, to high stress owing to the various hydraulic pressures at this part of the gasket. This stress Causes considerably hydraulic flow in the vicinity of the latter and due to this rapid wear and tear of the gasket.

It is the object of the present invention to improve geared hydraulic apparatus as hereinbefore incorporating means capable of eliminating the leakages without changing the counter-balancing of hydraulic pressure of the two side-plates in order to substantially increase the volumetric efficiency of the apparatus.

With this object in view, the apparatus according to the invention is characterised in that each of the two side-plates has, opposite each of the two passages formed between the side-plate and the adjacent cover by the third gasket and the two first gaskets which defines the region in which the pressure is highest, a sealing plug mounted to slide in a fluid-tight manner in a blind hole in the side-plate and urged to bear with a predetermined force against the cover adjacent the latter in order to close the corresponding passage.

Preferably, the blind hole is disposed at a location in which, during operation, there appears a relatively high pressure similar to that prevailing in the region of highest pressure.

During operation, an arrangement of this type ensures effective closure of the aforementiond passages without jeopardising the counter-balancing of the sideplates. During tests carried out on prototypes provided with this arrangement, the Applicant ascertained that the latter made it possible to increase the volumetric efficiency from the maximum value of obtained previously to a value close to 99% for a discharge pressure of I00 bars. With such volumetric efficiencies, it will be understood that it becomes possible to envisage the use of such apparatus as a hydraulic pump with a view to obtaining very high discharge pressures, for example of the order of 300 to 400 bars, which it was practically impossible to obtain with previous such apparatus.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a sectional view of an apparatus according to the invention,

FIG. 2 is a view on line II-II of FIG. 1,

FIG. 3 is an elevation on line IIlIll of one of the side-plates used in the apparatus of FIG. 1, and

FIG. 4 is a sectional view on line IVIV of FIG. 3.

In the drawings, the reference 10 designates a hydraulic apparatus of the said geared type intended to be used either as a pump or as a motor. The apparatus 10 is essentially constituted by two co-operating toothed wheels 12 and 14 respectively fixed to a driving shaft 16 and a driven shaft 18. The two shafts 16 and 18 are rotatably supported on either side of the set of wheels 12 and 14 by two side-plates 20 and 22 providing bearings and kept in abutting relationship, as explained hereafter, with the opposed side faces of the wheels 12 and 14. The arrangement constituted by the wheels 12 and 14 and the side-plates 20 and 22 is spectacle shaped (see FIG. 3) and is mounted in a cylindrical recess 24 of corresponding shape provided in the body 26 of the apparatus. The body 26 comprises an intake passage (not shown) and a discharge passage (not shown) both opening into the recess 24, in the region of the narrow part of the spectacle shaped arrangement at right angles to the plane of symmetry of the apparatus passing through the axes of rotation of the two wheels 12 and 14. The recess 24 is closed at these ends by two covers 28 and 30 secured to opposed side of the body 26 by positioning pins 32 and screws 34.

A hydraulic circuit for the circulation of low pressure fluid of the type described in the aforesaid French Patent Specification'is provided for lubricating the bear- 'ings 36 provided in" the side-plates 20 and 22 for the shafts l6 and 18. A circuit of this type consists of-circulating the low pressure fluid contained in each of two recesses 38 in each cover 28 and 30 through a set of four helical grooves 4 provided in each of the bearings 36 in the side-plates 20 and 22 and of returning the fluid thus used through conduits 42 to the recesses 38 which are in turn connected to an appropriate source of low pressure fluid (not shown). When the apparatus is' used as a pump, this source may advantageously be constituted by the intake of the apparatus.

As shown in more detail in FIG. 2, each of the two covers such as 30 is provided on its inner side with four closed grooves 44, 46, 48 and 50, in which are inserted corresponding annular gaskets 52, 54, 56 and 58 preferably of circular section.

Only the outer gasket 52, compressed against the body 26, ensures the fluid-tightness of the recess 24 as regards the ambient medium. I

The gaskets 56 and 58 partly compressed against the body 26 and partly against the s ide-plate such as 22 define two independent pressure regions 60 and 62 respectively connected to the intake and discharge orifices (not shown) of the .body 26.

The gasket 54 also partly compressed against. the body 26 and partly against the side-plate such as 22 surrounds the gaskets 56 and 58. It firstly defines with the latter, a central low pressure region 64 connected to the recesses 38 and secondly, with the gasket 52, an outer pressure regin 66 connected by axial channels 68 provided in the side-plate such as 22 to a part of the apparatus 10 in which an intermediate pressure between the intake pressure and the discharge pressure devel- If the abovedescribed apparatus 10, is used as a pump for example, then during operation, leakages would occur from the relatively high pressure space provided between each of the side-plates and 22 and the adjacent walls of the recess 24, towards the low pressure region 64. In fact, the gasket 54 and the gasket 58 defining the discharge region 62, which is thus at high pressure (pump outlet) form, between each side plate and the adjacent cover, two passages 70 of slight but not negligible section through which the aforesaid leakages occur.

If the appartaus 10 is used as a motor and assuming the same connections as those described above, similar leakages would occur through the passages 72 formed between the gasket 54-and the gasket 56 defining the intake region 60 which is thus at high pressure.

In order to eliminate the leakages, each of the sideplates 20 and 22 of the apparatus according to the invention is provided, as shown in FIGS. 3 and 4, with in the side face of each of the side-plates 20 and 22 opposite that adjacent the gear train 12 and 14. Each hole 78 is connected by a channel 80 to the space between the corresponding side-plate 20 and 22 and the cylindrical walls of the recess 24, and more precisely, to the part of this space whichis located immediately in the vicinity of the corresponding pressure region 60 or 62, namely upstream of the region in which the pressure is highest.

At the time of operation, when the apparatus 10 is used as a pump and assuming that the shaft 16 is driven in the direction shown in FIG. 2, the fluid pressure developed by the co-operation of the wheels 12 and 14 passes through channels 80 to the, blind hole 78 in which the plugs 74 slide. The latter, under the effect of this pressure, bear against the adjacent cover 28, 30 in order to block the leakage passage at A.

It should be noted that the action on the plugs 74 by the pressure developed at a predetermined point of the recess 24 makes it possible not to jeopardise the counter-balancing effect of the side-plates 20 and 22 by the gaskets 52, 54, 56 and 58.

When the apparatus 10 is used as a motor, it is necessary to reverse the roles of the plugs 74 and 76 if we assume the illustrated direction of rotation of the shafts 16 and 18.

It will also be noted that the symmetrical arrangement of the gaskets 52, 54, 56 and 58 as well as those of the plugs 74 and 76 with respect to the plane passing through the axes of rotation of the wheels 12 and 14 makes the apparatus 10 reversible either as a motor or as a pump. I

I claim:-

1. A geared hydraulic apparatus comprising:

a body defining a central recess, covers secured to opposite ends of said body to close the ends of said recess, and an outer gasket between each cover and its respective end of said body for providing a fluid-tight seal between said body and each cover, said body having fluid inlet and discharge ports,

two spaced apart side plates within said recess, each side plate being adjacent to one of said covers,

two cooperating toothed wheels within said recess and mounted on shafts rotatably supported in bearings carried by said side plates,

three gaskets arranged between the inner face of each cover, on the one hand, and its respective side plate and body end, on the other hand, said gaskets all being surrounded by said outer gasket and including two spaced apart inner gaskets and an intermediate gasket surrounding said inner gaskets,

said inner gaskets surrounding two independent regions connected to the inlet and discharge ports, respectively, of said body, said inner gaskets defining between them a region of low pressure connected to means for lubricating the shaft bearings, said intermediate gasket defining between itself and said outer gasket a region of intermediate pressure connected to said recess, and said intermediate gasket defining a passageway between itself and each of said inner gaskets,

a blind hole in each side plate opening toward its respective cover, and a plug arranged to slide in fluidtight manner within said hole, and

means for urging said plug toward said cover to seal said low pressure region from the one of said passageways adjacent to the one of said inner gaskets surrounding a high pressure region.

2. A geared hydraulic apparatus as defined in claim 1 wherein each side plate is formed with two blind holes, one opposite each of said two passageways, and a plug arranged to slide in fluid-tight manner within each hole,- and said urging means urges only the one of said plugs opposite the passageway containing higher pressure to seal that passageway from the low pressure region. whereby the apparatus is reversible.

3. A geared hydraulic apparatus as defined in claim 1 wherein each side plate is formed with four blind holes, a pair of said holes opposite each of said two passageways, each hole of each pair being opposite one end of its respective passageway. and a plug arranged to slide in fluid-tight manner within each hole. and said urging means urges only the two of said plugs opposite the passageay containing higher pressure to seal the ends of that passageway from the low pressure region,

of the recess wherein the fluid pressure is highest. 

1. A geared hydraulic apparatus comprising: a body defining a central recess, covers secured to opposite ends of said body to close the ends of said recess, and an outer gasket between each cover and its respective end of said body for providing a fluid-tight seal between said body and each cover, said body having fluid inlet and discharge ports, two spaced apart side plates within said recess, each side plate being adjacent to one of said covers, two cooperating toothed wheels within said recess and mounted on shafts rotatably supported in bearings carried by said side plates, three gaskets arranged between the inner face of each cover, on the one hand, and its respective side plate and body end, on the other hand, said gaskets all being surrounded by said outer gasket and including two spaced apart inner gaskets and an intermediate gasket surrounding said inner gaskets, said inner gaskets surrounding two independent regions connected to the inlet and discharge ports, respectively, of said body, said inner gaskets defining between them a region of low pressure connected to means for lubricating the shaft bearings, said intermediate gasket defining between itself and said outer gasket a region of intermediate pressure connected to said recess, and said intermediate gasket defining a passageway between itself and each of said inner gaskets, a blind hole in each side plate opening toward its respective cover, and a plug arranged to slide in fluid-tight manner within said hole, and means for urging said plug toward said cover to seal said low pressure region from the one of said passageways adjacent to the one of said inner gaskets surrounding a high pressure region.
 2. A geared hydraulic apparatus as defined in claim 1 wherein each side plate is formed with two blind holes, one opposite each of said two passageways, and a plug arranged to slide in fluid-tight manner within each hole, and said urging means urges only the one of said plugs opposite the passageway containing higher pressure to seal that passageway from the low pressure region, whereby the apparatus is reversible.
 3. A geared hydraulic apparatus as defined in claim 1 wherein each side plate is formed with four blind holes, a pair of said holes opposite each of said two passageways, each hole of each pair being opposite one end of its respective passageway, and a plug arranged to slide in fluid-tight manner within each hole, and said urging means urges only the two of said plugs opposite the passageay containing higher pressure to seal the ends of that passageway from the low pressure region, whereby the apparatus is reversible.
 4. A geared hydraulic apparatus as defined in claim 1 wherein said urging means includes a channel connecting said blind hole to a region within said body which contains a high pressure when the apparatus is in operation.
 5. A geared hydraulic apparatus as defined in claim 4 wherein said channel communicates with a region of the recess in said body which is upstream of the region of the recess wherein the fluid pressure is highest. 